Hot-swap Storage

I recently had to decommission an old Linux server and replace it with a new machine. When I was about to turn it off I noticed a power cable of the type used for IDE hard drives leaving the Linux server and entering an NT server that was in the same rack! It turned out that a DAT tape drive used for backup had been shipped without a power cable and they had been forced to take power from another machine. Incidentally is this likely to risk hardware damage?

So I had to take the NT machine down to fix it. The new cable had arrived so all I had to do was install it. One thing that wasn’t mentioned on the documentation was that the cable was designed to operate as a double-adapter and replace an existing cable. Once the phone support people had explained this (IBM support is really good – they solved the problem well within the SLA) I was able to correctly wire it.

However correct wiring in this case meant having a power cable go through the side of the storage bay and a SCSI cable came from the back of the case underneath the cooling fan assembly (something like 16 separate hot-swap fans in one assembly that can be removed for maintenance). The DAT drive took up space that could otherwise have been used for three hot-swap SCSI hard drives.

What I would like to know is, why can’t they make hot-swap DAT drives that use the same power and SCSI connectors as the hard drives? I don’t expect a DAT drive to be any more reliable than a hard drive, and when the system backup is mission-critical then down-time is required for a replacement. Not to mention the effort involved in the installation, my fingers are significantly longer than average, I can’t imagine how anyone with average size hands could complete the job!

So IBM, congratulations on the great phone support. But please try and make everything hot-swap when designing servers. Also while on the topic, I think that servers should be designed with external DVD drives connected via USB. I really hate it when I’ve got 10 * 2U servers in a rack, my system performance is limited by the number of disks and every single server has space that could be used for at least one disk sitting idle because there is a DVD drive gathering dust. For the IBM 2U servers in question, they could design them with space for 12 disks or 9 disks and one DAT drive which were all hot-swappable if they were smart about it, the current design supports 6 disks or 3 disks and a DAT.

You might consider something like an IBM BladeCenter; it holds many individual blade servers, and just a single CD/DVD drive which you can attach to a blade by hitting the “CD” button on that blade. Same with the console; hit a button to choose where the output goes.

> For the IBM 2U servers in question, they could design them with space for 12 disks or 9 disks and one DAT drive which were all hot-swappable if they were smart about it, the current design supports 6 disks or 3 disks and a DAT.